Questions:
How many BTC are left at the hands of the Trustee?
Will the trustee begin dumping again as in 2018 if the draft fails?
Why would the bankruptcy procedure drop the value of the coins to $485? This sounds irrational.
The BTC assets have appreciated since then, it is not so difficult to adjust the asset price in USD or Yen terms.
As of March 24, 2021 (date of 6th creditors meeting) the reported amount of BTC held by the Rehabilitation Debtor is 141,686.36882176 BTC, while the amount of BCH is 142,846.36249044.
The trustee may possibly sell some of those coins, if creditors ask for repayment in cash (rather than in cryptos) for an overall amount which exceeds available fiat assets.
Regarding those $485 per bitcoin, that's the rate that was fixed as the bankruptcy proceeding started, back in 2014. The rehabilitation plan is a later attempt by creditors to reach an agreement on a more fair distribution scheme, which takes into account the appreciation of BTC you correctly mentioned.
The point is, should the rehabilitation plan fail to get the majority of votes, then the bankruptcy proceeding would resume exactly as stated in the beginning, including that (now) ridiculously low BTC/USD rate.
In short: if you want to get a decent amount of your claim back, then please vote YES!